1. Field of the Invention
This invention relates to compositions and methods for controlling pest, and, more particularly, to pesticides that are derived from natural substances, such as plant alkaloids.
2. Description of Related Art
Infestation of pests continues to threaten the health of humans and animals, and causes damages to plants, wood structures and households. In particular, some 10,000 species of the more than 1 million species of insects are crop-eating, and of these, approximately 700 species worldwide cause most of the insect damage to man""s crops, in the field and in storage.
Our ancestors have used a wide variety of natural materials to protect plants from insects since 1000 B.C. For example, the earliest records of insecticides pertain to the burning of xe2x80x9cbrimstonexe2x80x9d (sulfur) as a fumigant. Even gall from green lizard was used to protect apples from worms and rot. Later, whitewash, lye, brine, vinegar, extracts of pepper and tobacco, and fish oil were used to control pests and repel biting and tickling insects.
Since the World War II (1940), attention has been focused on synthetic pesticidal chemicals that can be synthesized economically and used in large amounts to control insects on plants and in households. Thomson WT (1998) Agriculture Chemicals, Book I, xe2x80x9cInsecticidesxe2x80x9d, Thomson Publications, Fresno, Calif. These synthetic organic insecticides can be classified into many types of chemicals, including organochlorines, organophosphates, organosulfurs, carbamates, formamidines, dinitrophenols, organotins, pyrethroids, nicotinoids, spinosyns, fiproles, pyrroles, pyrazoles, pyridazinones, quinazolines, and benzoylureas.
The organochlorines are insecticides that contain carbon, hydrogen, and chlorine. The oldest group of the organochlorines is the diphenyl aliphatics, which included DDT, DDD, dicofol, ethylan, chlorobenzilate, and methoxychlor. More than 4 billion pounds of DDT were used throughout the world, beginning in 1940, and ending essentially in 1973, when the U.S. Environmental Protection Agency canceled all uses. Other organochlorines include hexchlorocyclohexane (HCH), cyclodienes, and polychloroterpens.
The organophosphates (OPs) are the most widely used synthetic pesticidal chemicals. Other names that are known for this type of pesticide are organic phosphates, phosphorus insecticides, nerve gas relatives, and phosphoric acid esters. All organophosphates are derived from one of the phosphorus acids, and as a class are generally the most toxic of all pesticides to vertebrates. Because of the similarity of OP chemical structures to the xe2x80x9cnerve gasesxe2x80x9d, their modes of action are also similar. Their insecticidal qualities were observed in Germany during World War II in the study of the extremely toxic OP nerve gases sarin, soman, and tabun.
The OPs have two distinctive features: they are generally much more toxic to vertebrates than other classes of insecticides, and most are chemically unstable or nonpersistent. It is this latter characteristic that brought them into agricultural use as substitutes for the persistent organochorines.
The OPs work by tying up or inhibiting certain important enzymes of the nervous system, namely cholinesterase (ChE). The enzyme is shown to be phosphorylated when it becomes attached to to the phosphorous moiety of the insecticide, a binding that is irreversible. This inhibition results in the accumulation of acetylcholine (ACh) at the neuron/neuron and neuron/muscle (neuromuscular) junctions or synapses, causing rapid twitching of voluntary muscles and finally paralysis.
The OPs, originally developed as nerve gases during the World War II, can impose serious dangers to people exposed to this type of chemicals. The OPs attack the brain and nervous system, even short-term exposure can cause damage. Symptoms include headaches, nausea, dizziness, seizures, and in extreme cases can result in paralysis, coma, and death.
Safer pesticides have been derived from plants such as tobacco, pyrethrum, derris, hellebore, quassia, and camphor. In particular, pyrethroids, synthetic or extracted from chrysanthemum, are widely used as insecticides in many countries.
Unfortunately, long-term use of a single type of pesticides that have similar mechanisms of action can result in pesticide resistance and resurgence of pests. Resistance and resurgence of pests represents a major problem in agriculture. To date, more than 500 species, including rats, mice, German cockroaches, mosquitos, Drosphilia melanogaster, and tobacco bud worms, are known to have developed resistance to the toxic effects of a variety of pesticides. Pesticide resistance is characterized by multiple mechanisms including increased detoxification, reduced absorption of applied pesticides, increased tolerance of the pesticide by the targeted pest, and increased elimination by the pest of the applied pesticide. Such resistance interjects elements of uncertainty when applying pesticides to target pest and can require a regimen of increasing application rates or ever-changing pesticides to overcome or prevent the development of resistance. Increasing the amount, frequency or rate of pesticide application, in turn, can generate a more serious problem of accumulating residual pesticide on plants and environmental contamination as to soil, air, and water.
The present invention provides novel compositions and methods for controlling pests, in particular, for killing insects that cause harmful effects to plants, wood, and animals. The compositions of the present invention may be used as a pesticide to prevent and protect plants from damages caused by insects, to prevent and reduce damages caused by termite to wood structures, and to protect and cure animals infested with harmful insects and microorganisms.
The compositions of the present invention comprise cocktails of plant alkaloids that are combined to exert its insecticidal activity via multiple pathways of signal transduction. The alkaloids in the compositions possess a variety of structures and functions which may contribute to the synergistic lethal effects of the compositions on a broad spectrum of insects.
In one embodiment, the composition of the present invention comprises: anabasine; and one or more plant alkaloids selected from the group consisting of toosendanin, azadirachtin, tomatine, nicotine, matrine, oxymatrine, sophocarpine, N-oxysophocarpine, cytisine, and aloperine. Optionally, the composition comprises two, three, four or more members of this group.
According to the embodiment, the alkaloid anabasine may be chemically synthesized. Alternatively, anabasine may be extracted from plants such as Anabasis aphylla, Nicotiana acuminata, Duboisia myoporoides, Zinnia elegans, and Zollikoferia eliquiensis. When extracted, anabasine may be in a pure form, a semi-purified form, or may be a component of an unpurified plant extract.
Also according to the embodiment, the one or more plant alkaloids may be chemically synthesized. Alternatively, the one or more plant alkaloid may be extracted from plants. When extracted, they may be in a pure form, a semi-purified form, or may be a component of an unpurified plant extract.
For example, toosendanin may be extracted from the plants Melia toosendan Sieb. et Zucc. and Melia azedarach L. Azadirachtin may be extracted from the plant Melia azedarach L. Tomatine may be extracted from Lycopersicon esculentum. The alkaloids, matrine, oxymatrine, sophocarpine, and N-oxysophocarpine, may be extracted from the plants Sophora flavescens Ait., and Sophora alopecuroides L. Cytisine and aloperine may be extracted from Sophora alopecuroides L.
In a variation of the embodiment, the composition further comprises a plant alkaloid selected from the group consisting of ricinine, harmaline, stellerin, euphol, triptonide, tripdiolide, and triptolide.
According to the variation, the plant alkaloids may be synthesized chemically, or extracted from plants. For example, ricinine may extracted from Ricinus communis L. Harmaline may be extracted from Peganum harmala L. Stellerin and euphol may be extracted from Stellera chamaeiasme L. The alkaloids, triptonide, tripdiolide, and triptolide, may be extracted from Tripterygium Wilfordii Hook F.
In one particular variation, the composition comprises: anabasine, toosendanin, and one or more alkaloids contained in the plant Sophora alopecuroides L. such as matrine, oxymatrine, sophocarpine, N-oxysophocarpine, cytisine, and aloperine.
In another particular variation, the composition comprises: anabasine, nicotine and toosendanin.
In another embodiment, the composition of the present invention comprises: harmaline; and one or more plant alkaloids selected from the group consisting of toosendanin, azadirachtin, tomatine, nicotine, anabasine, matrine, oxymatrine, sophocarpine, N-oxysophocarpine, cytisine, and aloperine. Optionally, the composition comprises two, three, four or more members of this group.
In yet another embodiment, the composition the pesticide of the present invention comprises: toosendanin, stellerin and one or more alkaloids contained in the plant Sophora alopecuroides L. such as matrine, oxymatrine, sophocarpine, N-oxysophocarpine, cytisine, and aloperine.
In yet another embodiment, the composition of the present invention comprises: toosendanin, harmaline and one or more alkaloids contained in the plant Sophora alopecuroides L. such as matrine, oxymatrine, sophocarpine, N-oxysophocarpine, cytisine, and aloperine.
In any of the above embodiments, the composition may further comprise an alkaloid selected from the group consisting of syemonine, aconitine, rotenone, and arteannuine.
These alkaloids may be synthesized chemically or extracted from plants. For example, syemonine may be extracted from Radix stemonae. Aconitine may be extracted from the plants Aconitum kusnezoffii reichb and Common monkshood mother root. Rotenone may be extracted from the plant Derris trifoliate lour. Arteannuine may be extracted from the plant Herba artemisiae annuae.
In any of the above embodiment, the composition may further comprise a solvent. Any solvent may be used to dissolve or disperse the composition, preferably a solvent that is generally regarded as safe (GRAS) for agriculture and household uses. Examples of solvents that may be used include, but are not limited to, pentane, hexane, heptane, octane, nonane, decane, isooctane, cyclohexane, petroleum distillates, petroleum ether, benzene, toluene, chlorobenzene, benzaldehyde, xylene, butanol, pentanol, hexanol, kerosene, diesel, turpentine and mixtures thereof.
In a preferred embodiment, the solvent for the composition is turpentine.
In any of the above embodiments, the pesticide may further comprise an emulsifier or a surfactant. Any emulsifier may be used to enhance the solubility and/or stabilize the composition, preferably an emulsifier that is generally regarded as safe (GRAS) for agriculture and household uses.
Optionally, the composition may further comprise a combination of emulsifers with complementary hydrophilic and hydrophobic parameters. For example, the emulsifiers may be a combination of nonionic surfactant and anionic surfactant.
Examples of nonionic surfactant include, but are not limited to, polyoxyethylated alkylphenols (e.g., octylphenol and nonylphenol), polyoxyethylated sorbitan monoesters, polyoxyethylated fatty or aryl-alkyl alcohols, fatty acids and esters (e.g. TWEEN(copyright) 40-80).
Examples of anionic emulsifier include, but are not limited to, alkyl, alkyl-aryl and aryl sulfonates, sulfates and phosphates, soaps (i.e., salts of carboxylic acids with at least 8 carbon atoms).
Optionally, the compositions may comprise an acidifying agent, an alkaline agent, an antioxidant, or any other agent which may be used to enhance the chemical stability of the alkaloids included in the composition.
In any of the above embodiments, the composition may comprise one or more solid agents for creating a dry, solid pesticide, or for timed release of the composition, such as powder, dust, microspheres, or pellets. These formulations may be used to stabilize the alkaloids prior to dilution with a solvent or may serve to allow the application of the composition to plants as a solid.
The concentration of each alkaloid in the composition before dilution and application may preferably be between about 0.1%-10% (w/v), more preferably between about 0.2%-2% (w/v), and most preferably between about 0.4%-1% (w/v).
The stability of the composition before dilution and application may preferably be between 80-100%, more preferably 90-100%, and most preferably 95-100% retained pesticidal activity after two years of storage at room temperature.
The compositions of the present invention can be used to protect plants, wood, and animals from harmful effects of insects. The composition may be diluted with water or other solvent and sprayed to crop plants indoor, inside a greenhouse, in a garden, and in the field. The composition may also be fumigated to kill insects in a closed environment or in the field. In addition, the composition may also be used to bath livestock and pets to kill insects that infested these animals. The composition may also be used to dust plants and fields.